Anatomie. — Biologie. 339 



recouvrant un meristeme general, primitif aussi, mais homogene- 

 A une petite distance du sommet un meristeme prevasculaire se 

 differencie aux depens du meristeme general; en coupe transversale 

 ce meristeme prevasculaire est reconnaissable ä la petitesse de ses 

 elements cellulaires et il affecte la forme soit d'un anneau, soit d'un 

 cercle plein. 



Ce qui reste du meristeme general en dehors d'un meristeme 

 prevasculaire constitue toujours l'ecorce primitive; ce qui reste au 

 dedans, lorsqu'il y a un reste, constitue la moelle primitive. 



L'dcorce et la moelle ne sont donc individualisees qu'ä une" 

 certaine distance du sommet. Leur individualisation n'est jamais 

 propre et elles peuvent 6tre considerees comme representant con- 

 stamment de simples restes du meristeme general primitif, c'est-ä- 

 dire des portions de celui-ci qui ne sont pas transformees en meri- 

 steme prevasculaire. M. J. Sirks (Wageningen). 



Me Cormick, F. A., Notes on the anatomy oftheyoung 

 tuber of Ipomoea Batatas Lam. (Botan. Gazette. LXI. p. 388 — 398. 

 8 Fig. 1916.) 



The larger roots of /. Batatas Lam. are polyarch, chiefly pen- 

 tarch and hexarch. 



Secondary thickenings occur in the usual way and there is 

 formed a massive structure of secondary xylem. 



Secondary cambiums are organized around Strands of xylem 

 and phloem which are separated by thin-walled parenchymatös 

 cells. The primary and secondary cambiums are capabJe of forming 

 xylem and phloem in isolated Strands. One may reasonably expect 

 that, if the conditions for growth are especially favorable, the se- 

 condary cambiums may be organized earlier. 



A section of a mature tuber shows a structure consisting 

 chiefly of parenchyma, and mingled with the parenchyma are 

 Strands of xylem, which consist of one to several vessels, and may 

 or may not be accompanied by phloem. Each Strand is surrounded 

 by a cambium. There may also be seen Strands of phloem unac- 

 companied ;by xylem. This structure may be definitely traced 

 back to the radial protostele. Jongmans. 



Gates, F. C, Xerofotic movements in leaves. (Botan. Ga 

 zette. LXI. p. 399—407. 8 Fig. 1916.) 



Xerofotic movements are paratonic movements, caused by un- 

 equal 'drying effects in direct sunlight, manifested by an upward 

 bend in leaflets or a curling upward of the blade. Greater turgor 

 of the cells of the lower side causes a movement in the direction 

 from which the desiccating energy comes. The xerofotic position 

 decreases the amount of direct radiant energy received per unit 

 area of leaf, reducing the harmful action of intense sunlight upon 

 the Chlorophyll as well as checking transpiration. 



Two classes of xerofotic response were noted. In the localized 

 type the differential turgidity acts in a limited region, such as in 

 tbe pulvini of leguminous leaflets. In the generalized type the 

 difference in turgidity is between the upper and lower part of the 

 blade. The localized response was characteristic of all observed 

 species of Leguminosae, but is not limited to that family. The 



